Specifically, supercritical carbon dioxide extraction of corn germ oil from corn germ utilizing extraction conditions adapted to a dry corn fractionation ethanol production process. Generally, inventive supercritical carbon dioxide extraction conditions which can be applied to corn germ.
As shown in FIG. 1, conventional ethanol production systems (1) may mill whole corn (2) into a mixture of corn particles (3) (referred to hereinafter as “milled corn”) the mixture of particles including corn bran, corn endosperm and corn germ. The milled corn (3) can be transferred to the ethanol production process (4) which includes the conventional steps of fermentation, distillation, and dehydration to generate an amount of ethanol (5). In the fermentation step, the milled corn (3) may be combined with an amount of water and an amount of alpha-amylase (or other enzyme capable of liquefying corn starch) to generate a mash in which the starch of the corn endosperm is liquefied. The mash may be held for a period of time at a temperature of between about 120 degrees Celsius (° C.) and about 150° C. to kill bacteria in the mash. The mash may then be held at a temperature of between about 90° C. and about 100° C. for a duration of time sufficient to achieve a desired level of liquefication of the starch. An amount of gluco-amylase (or other enzyme capable of generating fermentable sugars from the liquefied starch) added to the mash converts the liquefied starch to fermentable sugars, such as dextrose, in a process referred to as saccharification. Yeast can then be added to the mash to convert the sugars to an amount of ethanol (5) and an amount of carbon dioxide (6) (also referred to as “CO2”) along with other volatile organics. The amount of carbon dioxide (6) can be placed in a storage unit (18) or sold in the marketplace. For sale into certain markets or for certain applications, the amount of carbon dioxide (6) can be stripped of the other volatile organics and captured as an amount of purified carbon dioxide (9). The fermented mash often referred to as “beer” comprises an amount of ethanol (5) in a concentration of about eight percent to about eighteen percent by weight, other liquids, and non-fermentable solids. The amount of ethanol (5) in the beer can be separated and concentrated to about 190 proof by conventional distillation techniques and dehydrated by application to molecular sieve to produce a dehydrated ethanol of about 200 proof. The about 200 proof ethanol may be combined with up to about five percent denaturant to generate an amount of fuel grade ethanol (10) which can be placed in the storage unit (18) and subsequently sold.
The stillage which remains after distillation of the beer can comprise an amount of liquid typically referred to as “thin stillage” and an amount of remaining solids typically referred to as the “distillers grains”. The thin stillage can be separated from the distillers grains (for example by centrifugation). The distillers grains can be dried by evaporation of the remaining thin stillage. The thin stillage can be concentrated by evaporation of water to generate a syrup containing about twenty percent solids to about sixty percent solids (also referred to as “condensed distiller soluble”). The syrup can be recombined with the dried distillers grains to generate an amount of distillers dried grain with solubles (7) (“DDGS”). The DDGS can be sold as animal feed (8).
Even though there is an increasing demand for fuel ethanol (10) worldwide and an increasing amount of research in ethanol production, there remain substantial unresolved problems with respect to conventional ethanol production.
A first substantial problem with the conventional ethanol production process above-described and referring again to FIG. 1 can be that the amount of thermal energy (11) (or energy Btus or Btus) utilized by the conventional ethanol production process (4), including the steps of fermentation, distillation and dehydration, and by-product handling, which results in about a gallon of fuel ethanol (5), and a corresponding amount of DDGS (7) and carbon dioxide (6) may utilize an amount of thermal energy (11) of between about 30,000 and 40,000 British thermal units (hereinafter “Btu”). This amount of thermal energy (11) is typically generated by burning a corresponding amount of fossil fuel (12) such as oil, coal oil, coal or natural gas.
To reduce the amount of fossil fuels (12) utilized to provide the amount of thermal energy (11) required for the ethanol production process (4), an amount of the DDGS (7) may be burned to produce a part of the amount of thermal energy (11) required as described by United States Patent Application No. 2003/0019736A1.
Alternately, referring to FIG. 2, U.S. Patent Application No. 60/838,642, hereby incorporated by reference, inventive dry mill kernel fractionation processes (17) which fracture kernels of grain (13), such as cleaned conditioned corn, and isolate process fractions which include the pericarp (also referred to as “bran”), the germ, and the endosperm can be utilized to reduce the amount of thermal energy (11) required by the ethanol production system (4) or to generate an amount of thermal energy (11) without the use of fossil fuels (12). As shown in FIG. 2, the isolated endosperm fraction (14) can be introduced into the ethanol production process (4) without substantial amounts of the germ fraction (16) or the bran fraction (15). By introducing only the endosperm fraction (14) into the ethanol production process (4) an increased amount of ethanol (5) and fuel ethanol (10) can be generated per unit of fermented material. As the amount of ethanol (5) per unit of fermented material increases, the amount of thermal energy (11) required to produce an amount of ethanol (5) decreases. However, use of the inventive dry mill kernel fractionation processes (17) described also generates an isolated germ fraction (16) and the isolated bran fraction (15) which must be further processed, placed in the storage unit (18), sold, or disposed.
Referring now to FIGS. 3 and 4, various embodiments of the inventive dry mill corn fractionation process (17) as described by U.S. Patent Application No. 60/858,107 and International Patent Cooperation Treaty Patent Application No. PCT/US06/45193, each hereby incorporated by reference, can utilize the isolated germ fraction (16) and the isolated bran fraction (15) (or isolated components thereof whether in whole or in part or separately or in various combinations) to generate an amount of thermal energy (11) to replace in whole or in part the amount of thermal energy (11) conventionally produced by burning fossil fuels (12). With respect to the corn germ fraction (16), extraction of the corn germ fraction (16) with an amount of supercritical carbon dioxide (28) can generate an amount of corn oil (23) which can be placed in the storage unit (18), sold, burned to produce thermal energy (11) or can be converted to biodiesel (27) which can placed in the storage unit (18), sold or burned as a fuel (33) to produce an amount of thermal energy (11) separately or in combination with an amount of any one or more of condensed distiller soluble (30), fusel oil (29), ethanol (5), or fractionated corn gluten meal (31). As to certain embodiments of the invention, the amount of thermal energy (11) can be transferred to a boiler (34) which can produce steam which coupled to a turbine (36) can generate an amount of electricity (37).
A substantial problem with respect to corn germ oil extraction (21) of the corn germ fraction (16) to produce an amount of corn germ oil (23) can be that conventional carbon dioxide extraction methods whether performed with carbon dioxide or with supercritical carbon dioxide utilize extraction conditions which: may not extract (21) a substantial portion of the amount of the corn oil (23) contained in the corn germ fraction (16), or may extract the amount of corn oil (23) contained in the corn germ fraction (15) at a rate which requires greater than about thirty minutes (the term “about” means greater or lesser than the value or range of values stated by 10 percent, but not does not limit any value or range of values to this broader definition and each value or range of values preceded by the term “about” also includes in the alternative the absolute value or range of values stated), or may not extract an amount of corn oil (23) from the corn germ fraction (16) of between about 18 weight percent to about 30 weight percent (such weight percent including any processing of the corn germ to remove a part of the oil prior to extraction with carbon dioxide or supercritical carbon dioxide), or may not extract 90 percent or more of the extractable amount of corn oil (23) in the amount of corn germ fraction (16)), or requires utilization of an amount of supercritical carbon dioxide (28) to the amount of corn germ fraction (16) extracted of greater than about 5 to 1 (wt./wt.) (as a non-limiting example, ratios of 5 to 1 or less may be preferred in certain embodiments of a dry mill corn fractionation process (17) in the context of ethanol production ), or of greater than about 7 to 1 (as a non-limiting example, ratios of 7 to 1 or less may be preferred in other embodiments of the dry mill corn fractionation process (17) in the context of ethanol production), or may greater than about than 12 to 1 (as a non-limiting example, 12 to 1 or less may be preferred in yet other embodiments of the dry mill corn fractionation process (17) in the context of ethanol production).
As such, conventional carbon dioxide extraction methods may be in whole or in part impracticable or incompatible with the process rates or efficiency rates required in the context of a dry mill kernel fractionation ethanol production process (17), or may not be competitive or commercially feasible relative to other conventional methods, or are simply less desirable to extraction conditions which allow between about 18 weight percent to about 30 weight percent of the corn germ fraction (16) (or greater weight percents for corn germ having greater weight percentage extractable corn oil such as about 45 weight percent corn germ oil) to be extracted as corn oil (23) utilizing a ratio of supercritical carbon dioxide (28) to corn germ fraction (16) of not greater than about 12.0 to 1 (wt./wt.), or not greater than 7 to 1, or not greater than 5 to 1, or of greater than 2 to 1 depending on the application. Understandably, the inventive corn germ fraction (16) extraction conditions described herein may confer an advantage in other applications outside of ethanol production systems (17) described herein or incorporated by reference and the invention is not so limited.
Now referring primarily to FIG. 4, another substantial problem with conventional methods of corn germ oil extraction (21) may be that the extracted corn germ fraction (22) (also referred to as “germ cake”) may contain an amount of water (25) subsequent to corn oil extraction (21), a portion of which may require evaporation or otherwise removed before the germ cake (22) prior to placement in the storage unit (18) or sold, or which increases the number steps to process the germ cake (22) into a particular germ cake byproduct (27) (such as a germ cake animal feed) or makes the steps to produce a particular germ cake byproduct (27) more costly. As an example, further described below, the condensed distiller soluble (24) above-described can be mixed with the germ cake (22) but the amount of water (25) contained by the germ cake (22) subsequent to mixing which is in excess of about fourteen percent by weight (or in excess of a pre-selected or desired amount of water) must be removed. As such, any reduction in the amount of water (25) contained by the germ cake (22) subsequent to corn oil extraction (21) can reduce the amount of water (25) that must be removed from the germ cake (22) or removed from a mixture of germ cake (22) and condensed distiller soluble (24) to achieve an amount of water in a germ cake animal feed (27) of less than fourteen percent by weight or other water content desirable based upon the application.
The present inventive supercritical carbon dioxide extraction conditions of the corn germ fraction (16) described herein address each of the above-mentioned problems related to conventional corn germ oil extraction from corn germ (16).